Camera tube with accurate field mesh mounting means

ABSTRACT

An improved camera tube of the vidicon type has a field mesh accurately mounted between the target and the electron beam gun. The mesh is mounted in a manner to permit accurate spacing and parallel alignment with the target surface and to permit external electrical connections with the field mesh to be made without disturbing the electrical fields within the tube, providing a low inductance contact to the mesh particularly useful in high resolution tubes.

United States Paten [1 1 French et a1.

CAMERA TUBE WITH ACCURATE FIELD MESH MOUNTING MEANS inventors: Raymond .1. French, East Syracuse;

Richard A. Wagner, West Monroe; Richard E. Zehr, North Syracuse, all of NY.

General Electric Company, Owensboro, Ky.

Filed: May 13, 1971 Appl. No.: 143,229

Related U.S. Application Data Continuation of Ser. No. 832,283, June 11, 1969, abandoned.

Assignee:

U.S. Cl 313/65 R, 313/285, 313/284 int. Cl. H01] 31/28, HOlj l/96, HOlj 29/02 Field of Search 313/65 A, 65 AB,

References Cited UNITED STATES PATENTS 8/1961 Krieger et a1. 313/65 R [451 July 17, 1973 3,023,492 3/ 1962 Bristow 117/22 X 3,201,630 8/1965 Orthuber et al. 313/89 X 3,256,455 6/1966 Saldi 313/89 X 3,284,655 11/1966 Oess 313/89 X FOREIGN PATENTS OR APPLICATIONS 1,097,587 1/1968 Great Britain 313/65 A Primary Examiner-Robert Sega] Attorney-Nathan .I. Cornfeld, John P. Taylor et al.

An improved camera tube of the vidicon type has a field mesh accurately mounted between the target and the electron beam gun. The mesh is mounted in a manner to permit accurate spacing and parallel alignment with the target surface and to permit external electrical connections with the field mesh to be made without disturbing the electrical fields within the tube, providing a low inductance contact to the mesh particularly useful in high resolution tubes.

ABSTRACT 5 Claims, 3 Drawing Figures Patented July 17, 1973 3,746,917

INVENTORS: RAYMOND J. FRENCH, RICHARD A. WAGNER,

RICHARD E. ZEHR,

BYM V THEIR ATTORNEY.

CAMERA TUBE WITH ACCURATE FIELD MESH MOUNTING MEANS This is a continuation of Ser. No. 832,283, filed 6/1 1/69 now abandoned.

BACKGROUND OF THE INVENTION This invention relates to camera tubes, particularly vidicon type camera tubes using a field mesh positioned between the electron beam gun and the target.

The use of a field mesh as a decelerating electrode placed between the beam gun and the target, usually as close to the target as possible, is well known. Such a structure is shown for example in U. S. Pat. No. 3,321,655 assigned to the assignee of this invention. The use of such a field mesh is also desirable to insure orthigonal landing of the beam on the target regardless of the position of the beam. To accomplish this function properly, the mesh should be accurately spaced parallel to, and immediately adjacent, the target and should be maintained at a positive potential with respect to the target potential.

The successful use of such a mesh has, however, been complicated, for example, in tube designs where it is desirable to extend the focus or deflection electrode means to a position close to the target for maximum beam control, leaving very little space for accurate placement of the mesh. Furthermore, if the inner wall of the envelope be used as a support for such electrode means and separate mesh potential operation is desired, electrical connections must be made to the mesh through the envelope wall to prevent interference with the electric fields present within the tube to control the focus and deflection of the beam.

It has been proposed to mount the grid on three pins thrust through the glass envelope and radially spaced about 120 apart. While this design provides the means for connecting the mesh to an externalpotential without interfering with the fields within the tube, accurate mechanical placement of the mesh in a plane parallel to the target plane is very difficult. Furthermore, distortion of the glass surrounding the pins prevents placement of the deflection or focus means as close to the mesh as would be desirable particularly when the glass envelope is used as the support for such electrodes.

It is therefore an object of this invention to provide a camera tube wherein a field mesh can be accurately mounted adjacent and parallel to a target. It is another object of the invention to provide a camera tube wherein the field mesh can be externally connected to an electrical potential source without interfering with the deflection fields within the tube and to provide a low inductance contact to the mesh. It is a further object of the invention to provide a camera tube wherein the deflection means can be mounted in close proximity to the mesh thus leavingvery little beam travel length from the deflection field influenced spaced to the target.

SUMMARY OF THE INVENTION In accordance with the objects of the invention a camera tube comprising an insulative envelope, having mounted therein an electron beam generating gun, means adjacent the envelope for controlling the deflection of the beam, target means within the envelope scanned by the electron beam, and a field mesh adjacent the target, is provided with a field mesh mounting means comprising first conductive terminal means peripherally engaging the envelope and supporting a mesh, a second conductive terminal means engaging the target, and an insulating spacer mounted between the first and second conductive terminal means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of a preferred embodiment of this invention.

FIG. 2 is a vertical, view of a portion of the tube of FIG. 1 partially cutaway to reveal a cross-sectional portion.

FIG. 3 is an enlarged and exploded view of a portion of FIG. 2.

DETAILED DESCRIPTION Referring now to FIG. 1, a camera tube is generally indicated at 2. Tube 2 comprises a generally cylindrical evacuated glass envelope 4 and has a faceplate 6 at one end of envelope 4. Faceplate 6 supports the target which in the illustrated tube in FIGS. 2 & 3 comprises a photoconducting layer 10 coated on the inside surface of faceplate 6. An electron beam generating means (not shown) is mounted within envelope 4 adjacent rear wall 8 and spaced apart from faceplate 6.

In the preferred embodiment illustrated, there are mounted immediately inside the envelope 4, or on the inside wall of the envelope itself between the electron beam generating means and faceplate 6 deflecting elec trodes 14 to control the scan of the electron beam across photoconducting layer 10. In the illustrated embodiment electrodes 14 are formed in a particular configuration for electrostatic deflection of the electron beam. When magnetic deflection is used, the inner wall of envelope 4 may be coated with a continuous metal layer.

In the illustrated embodiment the deflecting electrodes (or if magnetic deflection is used, the focus electrode) are extended along the axis of the envelope ter minating a short distance from faceplate 6 to afford maximum control over the beam throughout the flight path of the electrons from the electron beam generating means.

In accordance with the invention, field mesh 20, as best seenin FIGS. 2 & 3, is mounted parallel to and spaced from faceplate 6 in the spaced defined between faceplate 6 and the termination of electrodes 14. Field mesh 20 is mounted on a metal terminal ring 22 which is sealed to the end of glass envelope 4. A ceramic cylindrical spacer or washer 50 of approximately the same diameter as envelope 4 is then bonded at one end to terminal ring 22. A second terminal ring which carries faceplate 6 is then bonded to the opposite end of ceramic spacer 50.

Field mesh 20 comprises a finely divided mesh of about 1000 lines per inch. The mesh is peripherally mounted by welding or other suitable means to a metal terminal ring 22 comprising metal flange 24 and metal flange 30. Flange 24 has an upturned portion 26 which is welded to flange 30. Alternatively flanges 24 and 30 may comprise a unitary member. Flange 30 is formed with a horizontal portion 32, a downwardly turned outer lip 34 and an upwardly turned inner lip 36. Portion 26 of flange 24 is welded to an inner edge 38 of lip 36. Flange 30 in turn, is sealed to the end edge of cylindrical glass envelope 4 using conventional glass-tometal sealing techniques.

Ceramic spacer 50, which is cylindrical and generally of about the same diameter as envelope 4 is then bonded to shoulder 42 of flange 30. Ceramic spacer 50 can comprise any of a number of ceramic materials such as for example, forsterite, zircon, steatite, and alumina. High strength alumina having an aluminum oxide content of over 85 percent is preferred, however. The edges of spacer 50 are metalized to facilitate bonding of the ceramic to the metal rings. A suitable process for metalizing ceramic and which has been successfully used in the practice of this invention is described and claimed in Bristow U.S. Pat. No. 3,023,492 assigned to the assignee of this invention. The metalized ceramic is then bonded to flange 30 on terminal ring 22 by a suitable solder, such as, for example, a silver-copper alloy.

Similarly a metal terminal ring 60 having an upturned outer lip 62 and a downwardly turned inner lip 64 is bonded to an upper edge 52 of ceramic washer 50. Mounted to terminal ring 60 is glass faceplate 6 which is sealed thereto by conventional glass-to-metal sealing techniques. Faceplate 6, thus forms the end wall of camera tube 2.

Faceplate 6 has a photoconductive coating 10 applied on the inner surface. Faceplate 6 may be made of conducting glass or there may be a conducting layer interposed between the faceplate and photoconductive layer 10. The conductive glass, or conductive layer peripherally contacts metal terminal ring 60. After assembly of tube 2 external electrical connection is made to terminal ring 60 to establish the appropriate potential for the target.

Similarly metal terminal ring 22 is used to electrically connect mesh to an appropriate potential source to establish a beam guiding field between mesh 20 and target 10 to provide orthogonal landing of the electron beam on target 10. Ceramic washer 50 insulates terminal ring 22 from terminal ring 60 and, in cooperation with upper shoulder 42 of flange 30 and lower edge 66 of terminal ring 60, accurately spaces mesh 20 from target 10 and faceplate 6. Using the construction of the invention, mesh 20 can not only be accurately mounted parallel to target 10, but the distance therebetween can be predetermined and accurately maintained by proper choice of the height or thickness of ceramic washer 50.

The invention also permits, for example, when electrostatic deflection is used, accurate placement of appropriate deflecting electrodes on the inner surface of glass envelope 4, or immediately adjacent thereto, terminating a minute distance from mesh 20. Thus the beam is under the influence of the field produced by electrodes 14 for a maximum distance which is greater than that attainable using prior art constructions.

The invention permits external electrical connection to be made to the field mesh without producing glassdeforming punctures in envelope 4 which would prevent mounting electrodes 14 adjacent mesh 20. External electrical connection in turn obviates the need for internal fieldproducing electrical connection to the mesh which might interfere with the beam directing fields set up by electrodes 14. Furthermore the invention permits highly accurate mounting of the field mesh in parallel relationship to the target as well as providing means for accurately spacing the distance between the mesh and the target. While the field mesh terminal ring, the ceramic spacer, and the faceplate and target mounting terminal ring all form a part of the outer envelope of the tube they need not be heated to temperatures which would risk physical deformity when sealed to the glass envelope and to one another to provide an evacuated tube.

Thus the invention provides an improved camera tube having enchanced electrical properties and mechanical strength, which can be easily and economically constructed. While a preferred embodiment using electrostatic deflecting electrodes has been illustrated, it will be apparent to those skilled in the art that either magnetic or electrostatic or mixed focus and deflection fields can be used without departing from the scope of the invention. Other minor modifications of the illustrated embodiment will also be apparent to those skilled in the art and are to be considered within the scope of the invention provided by the appended claims.

What we claim as new and desire to be secured by Letters Patent of the United States is:

1. An camera tube comprising a cylindrical glass envelope having electron beam generating means therein adjacent one end of said envelope; target means therein spaced apart from said beam generating means, and electrode means therebetween on the inner wall of said envelope and terminating adjacent a point spaced from said target means, a first metallic ring sealed to said envelope immediately adjacent to said termination point of said electrode means on said wall, a second metallic ring having a glass faceplate sealed thereto carrying said target means; and a cylindrical ceramic spacer member between said rings having a diameter approximately that of said glass envelope and having metallized edges thereon bonded to said rings to provide accurate and parallel spacing between said mesh on said first ring and said target means carried by said second ring, each of said mounting rings having a flange contacting the entire adjacent surface of said ceramic spacer member and a portion of the inner surface thereof, said first ring having mounted thereon a mesh extending across an annular mounting ring having an upstanding flange welded to the inner surfacecontacting flange of said first ring, and providing means for electrically communicating with said mesh independent of the electrical field created by said electrode means on the inner wall of said envelope.

2. The assembly of claim 1 wherein said rings are bonded to said metallized ceramic edges by solder means.

3. The assembly of claim 1 wherein said elements are sealed to one another and to the glass envelope without physical deformity of said elements to insure maintenance of said accurate and parallel spacing between said mesh and said target means.

4. The assembly of claim 1 wherein said ceramic spacer comprises a material selected from the class consisting of forsterite, zircon, steatite, and alumina.

5. The'assembly of claim 1 wherein said ceramic spacer comprises a high strength alumina having an aluminum oxide content greater than percent. 

1. An camera tube comprising a cylindrical glass envelope having electron beam generating means therein adjacent one end of said envelope; target means therein spaced apart from said beam generating means, and electrode means therebetween on the inner wall of said envelope and terminating adjacent a point spaced from said target means, a first metallic ring sealed to said envelope immediately adjacent to said termination point of said electrode means on said wall, a second metallic ring having a glass faceplate sealed thereto carrying said target means; and a cylindrical ceramic spacer member between said rings having a diameter approximately that of said glass envelope and having metallized edges thereon bonded to said rings to provide accurate and parallel spacing between said mesh on said first ring and said target means carried by said second ring, each of said mounting rings having a flange contacting the entire adjacent surface of said ceramic spacer member and a portion of the inner surface thereof, said first ring having mounted thereon a mesh extending across an annular mounting ring having an upstanding flange welded to the inner surface-contacting flange of said first ring, and providing means for electrically communicating with said mesh independent of the electrical field created by said electrode means on the inner wall of said envelope.
 2. The assembly of claim 1 wherein said rings are bonded to said metallized ceramic edges by solder means.
 3. The assembly of claim 1 wherein said elements are sealed to one another and to the glass envelope without physical deformity of said elements to insure maintenance of said accurate and parallel spacing between said mesh and said target means.
 4. The assembly of claim 1 wherein said ceramic spacer comprises a material selected from the class consisting of forsterite, zircon, steatite, and alumina.
 5. The assembly of claim 1 wherein said ceramic spacer comprises a high strength alumina having an aluminum oxide content greater than 85 percent. 